Synthesis of α-Cobalt Hydroxides with Different Intercalated Anions and Effects of Intercalated Anions on Their Morphology, Basal Plane Spacing, and Capacitive Property

Abstract

The four α-cobalt hydroxides (green or blue) with different intercalated anions were synthesized by a chemical precipitation route in which polyethylene glycol was used as the structure-directing reagent for application in the electrode materials of electrochemical capacitors. Every one among the four samples displays an interesting and distinctive morphology although the synthesis conditions were the same except for the anions. The intercalated anions have a critical effect on the basal plane spacing, morphologies, and capacitive properties of the products. Structural and morphological characterizations were performed by using power X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The component and thermal stability of the sample were respectively measured by FT-IR and thermal analyses, including thermogravimetry (TG) and differential thermogravimetry (DTG). The electrochemical behaviors were measured by cyclic voltammogram and galvanostatic charge−discharge. The specific capacitance is up to 697 F g −1 at a charge−discharge current density of 1 A g −1 for the sample with intercalated chlorine. But the sample with intercalated sulfate, which has small crystalline size, more disordered structure, and almost perfect alveolate nanostructure with a large surface area, exhibits relatively poor specific capacitance (420 F g −1 ). The exceptive phenomena caused by intercalated anions were explained by hydrogen bonding and electrostatic forces. Moreover, the relationships between the specific capacitance, basal plane spacing, as well as the content of the interlayer water were discussed in detail for the four as-synthesized samples.